Lubricant compositions containing derivatives of anthranilic acid

ABSTRACT

Lubricants are stabilized against oxidative degradation by adding thereto a stabilizing amount of an ester of an anthranilic acid. An example of a suitable material is n-octyl Nnaphthylanthranilate (n-octyl N-phenyl-1-naphthyl-2&#39;&#39;carboxylate).

United States Patent Braid Dec. 24, 1974 LUBRICANT COMPOSITIONS 2,390,943 12/1945 Kavanagh et a1. 252 515 A CONTAINING DERIVATIVES 0 3,247,111 4/1966 Oberright et a1. 252/50 X 3,282,840 11/1966 Foster et al 252/515 A ANTHRANILIC ACID 3,642,632 2/1972 Coburn et a1... [75] Inventor: Milton Braid, Westmond, NJ. 3,767,575 10/1973 Braid 252/515 A X [73] Assignee: Mobil Oil Corporation, New York,

NY. Primary Examiner-Patrick P. Garvin Assistant Examiner-Andrew l-l. Metz [22] Flled' 1973 Attorney, Agent, or FirmAndrew L. Gaboriault; [21] Appl. No.: 337,185 Raymond W. Barclay; Claude E. Setliff Related US. Application Data [63] Continuation-impart of Ser. No. 126,891, March 22,

1971, abandoned. [57] ABSTRACT [52] us CL 252/515 A 252/403 Lubricants are stabilized against oxidative degradation [51] Int. Cl C 10m l/32 by adding thereto a Stabilizing amount of an ester of [58] Field of 252/51 5 A 403 an anthranilic acid. An example of a suitable material 'I is n-octyl N-naphthylanthranilate (n-octyl N-phenyI-l- [56] References Cited naphthyl-Z'-carboxylate).

UNITED STATES PATENTS 2/1945 Trautrnan 252/515 A 10 Claims, No Drawings LUBRICANT COMPOSITIONS CONTAINING DERIVATIVES OF ANTI-IRANILIC ACID CROSS REFERENCE TO RELATED APPLICATIONS This application is a continuation-in-part of US. application Ser. No. 126,891 filed Mar. 22, 1971 and now abandoned.

BACKGROUND OF THE DISCLOSURE 1. Field of the Invention This invention relates to the inhibition of oxidation in lubricants. More particularly, the invention has to do with lubricants in which have been placed an additive having the ability to reduce oxidation of such lubricant. Still more particularly, the additive of this invention may be referred to as an ester of an N-naphthyl anthranilic acid.

2. Discussion of the Prior Art Lubricants, such as lubricating oils and greases, are Subject to oXidative deterioration at elevated temperatures or upon prolonged exposure to the elements. Such deterioration is evidenced, in many instances, by an increase in acidity and in viscosity, and when the deterioration is severe enough, it can cause metal parts to corrode. Additionally, severe oxidation leads to a loss of lubrication properties of the lubricants, and, in especially severe cases, to complete breakdown of the device being lubricated. In combatting oxidation, many additives have been tried, but many of them are only marginally effective except at high concentrations, especially when the lubricant is subjected to drastic oxidizing conditions. I

There are patents which disclose certain anthranilic acid esters as antioxidants. US. Pat. Nos. 2,369,090 and 2,390,943 disclose methylanthranilate for this purpose in a petroleum or hydrocarbon oil. US. Pat. No. 2,369,090 also teaches the use of ethyl, propyl or butyl anthranilate. US. Pat. No. 3,642,632 is concerned with the C C alkyl anthranilates and those N-substituted anthranilates where the substituent is a C -C alkyl or SUMMARY OF THE INVENTION In accordance with the invention, there is provided a lubricant composition comprising a major amount of a lubricant and an amount sufficient to impart antioxidant properties thereto of an ester of an N-naphthyl anthranilic acid.

DESCRIPTION OF SPECIFIC EMBODIMENTS The anthranilic acid ester which is useful in the practice of this invention has the formula COOR an alkyl group having from 1 to about 20 carbon atoms and X is selected from the group consisting of hydrogen, halogen (e.g., chlorine, bromine, iodine, fluorine), alkoxy or alkyl of from about 4 to about 20 carbon atoms, nitro, and cyano.

In general, these compounds may be prepared in known ways from the appropriate carboxylic acid or acyl halide and alcohol. The esterification is not critical, and will depend largely upon the size and type of the alcohol being used. Thus the reaction can be run at fromabout 50C. to, but not including, the decomposition temperature of the product. In general, the temperature will range from about 50C. to about 250C.

It is generally preferred that an organic reaction medium be present during the reaction. Inert organic media may be used, in which case those including benzene, toluene, xylene, chlorobenzene and the like may be selected. In some instances it may be appropriate to use a large excess of the alcohol employed as the esterifying member.

When used as antioxidants, the products disclosed herein are effective at a concentration of from about 0.005 percent to about 15 percent by weight of the lubricant. Preferably, such concentration shall be from about 0.01 percent to about 10 percent by weight thereof, and more preferably from about 1.0 percent to about 5.0 percent by weight.

The compounds are useful in a variety of lubricants. Those which may be improved by adding an anthranilic acid ester thereto are mineral and synthesized lubricating oils, as well as greases made therefrom. The mineral oils will be understood to embrace not only the paraffinic, but also the naphthenic and aromatic-containing members. By synthesized oils are meant synthesized hydrocarbons, polyalkylene oxide oils, polyacetals, polysilicones and the like, as well as synthetic ester oils. Of the latter type there may be mentioned those esters made from monohydric alcohols and polycarboxylic acids, such as 2-ethylhexyl azelate and the like, and those made from polyhydric alcohols and aliphatic monocarboxylic acids. Those of this group are espe cially important, and they include esters prepared from the polymethylols, as for example the trimethylols, such as the ethane, propane and butane derivatives thereof, 2,2-disubstituted propane diols and the pentaerythritols with aliphatic monocarboxylic acids containing from about 4 to about 9 carbon atoms. Mixtures of these acids may be used to prepare the esters. Preferred in the practice of this invention are the esters prepared from a pentaerythritol and a mixture of C -C acids. In making such esters, a generally acceptable product can be made from commercial pentaerythritol containing about 88 percent of monopentaerythritol and 12 percent dipentaerythritol.

Having described the invention in general terms, the following is offered as a specific embodiment thereof. It will be understood that the example is merely for the purpose of illustration, and that there is no intention to limit the scope of the invention to the member shown.

EXAM PLE I l NH C O O CI-Ia CH CH(CH:1)2

2,2,4-Trimethylpentyl N-Naphthylanitranilate A mixture of 8.1 g. ofN-phenyl-1-naphthylamine-2'- carboxylic acid chloride, 4.7 g. of 2,2,4-trimethyl-1- pentanol and 100 ml of benzene was heated at reflux for 6 hours and filtered hot. The filtrate was extracted with percent potassium hydroxide solution, washed with water, and dried. Solvent and unreacted alcohol were removed by distillation. The ester product was obtained from the residue as viscous yellow oil.

AnaLCalcd for C H O N: C, 79.96: H, 7.78; N, 3.73 Found: C, 79.32; H, 7.69; N, 3.88

EXAMPLE 2 I NH C O O caHn-n AnaLCalcd for C H O N: C, 79.96; H, 7.7

Found: C. 80.31; H, 7.6

EXAMPLE 3 Methyl N-Naphthyl-4-Chloroanithranilate A solution of 28 g. of N-(5-chlorophenyl)-lnaphthylamine-Z'-carboxylic acid in 300 ml of methanol was refluxed at 68-74C. While a moderate gas stream of hydrogen chloride was passed through for about 4 hours. Excess methanol was distilled from the reaction mixture, the residue was taken up in ether and extracted with aqueous potassium hydroxide solution to remove unreacted carboxylic acid, and the ether solution was dried. The methyl ester of the acid was isolated from the residue after removal of the ether solvent as a crystalline solid mp. l18-l22C.

Anal. Calcd: N.

4. Found: N, 4

The following examples are offered for purposes of comparison.

EXAMPLE 4 NHz OOOCHa Methyl Anthranilate Made by conventional esterification of anthranilic acid with methanol and an acid catalyst.

EXAMPLE 5 COO CH2!) CHzC CH2CH(CH3)2 2,2,4-Trimethylamyl Anthranilate To 39 g. of 2,2,4-trimethyl-l-pentanol there was added 0.5 g. of sodium slivers and the mixture was heated at C. for several hours. The reaction mixture was cooled to 60C., unreacted sodium was removed, 45.5 g. of methyl anthranilate was added, and the mixture was heated at 90C. for 2 hours. Solids were removed by filtration. The anthranilic acid ester product was isolated from the filtrate by distillation as a pale yellow liquid, b.p. 149C. at about 1 mm.

AnaLCalcd for C H O N: C, 72.25; H, 9.30; N, 5.62 Found: C. 71.86; H. 9.02; N, 5.59

EXAMPLE 6 bllHz n-Octyl Anthranilate To a methanolic solution of sodium methoxide (prepared from 30 ml of methanol and 0.2 g. of sodium) were added 91 g. of methyl anthranilate and 78 g. of loctanol. The reaction mixture was heated at 90C. for 0.75 hour and at C for 0.75 hour while methanol was removed by distillation. The residue was washed with water, dried, and distilled. n-Octyl anthranilate was obtained as a clear liquid, b.p. 139l44C at about 0.5 mm.

Anal. Calcd for C, H O,N: C. 72.25; H, 9.30; N, 5.62 Found: C, 72.35; H. 8.98; N, 5.55

EXAMPLE 7 I|-IH2 C O CHiCHCHrCHiCH:

Z-Ethylhexyl Anthranilate By the method of Example 6, the reaction of 78 g. of 2-ethylhexanol and 91 g. of methyl anthranilate produced the ester 2-ethylhexyl anthranilate as a clear pale yellow liquid distillate fraction, b.p. 150-155C. at less than 1 mm.

Anal. Calc'd for C H O N: C, 75.25; H, 9.30; N. 5. Found: C, 72.98; H, 9.31; N, 5.

EXAMPLE 8 Anal. Caldd for C H O NI C, 77.50,

H, 8.36; N, Found: C, 77.0 H. 8.22; N,

EXAMPLE 9 O CH:

n-Octyl N-4-Methoxyphenylanthranilate By the method of Example 8, a mixture of 48.6 g. of N-4-methoxyphenylanthranilic acid, 130.2 g. of 1- octanol and 2 g. of p-toluenesulfonic acid was heated at 130C. for 3.25 hours. The ester n-octyl N-4-methoxyphenylanthranilate was obtained as a liquid distillate fraction, b.p. 230-235C. at less than 0.1 mm pressure.

Anal. Calcd for C H O N: C, 74.33

Found: C, 75.00;

EXAMPLE 10 c o 0-@- C(om).

p-tert-Butylphenyl Anthranilate To 112.5 g. of p-tertbutylphenol heated at l20C. there was added in portions 123 g. of isatoic anhydride during about 0.75 hour. The reaction mixture was allowed to cool and was then extracted with hot ethyl alcohol from which the crude ester crystallized upon cooling. Recrystallization from n-heptane afforded the crystalline ester mp l42'.143C.

Anal. Calc'd for C H O N: C. 75.81; H, 7.11; N, 5.20 Found: C. 75.75; H. 7.05; N. 5.32

EXAMPLE 1 1 IIIHCHa n-Oc'tyl N-Methylanthranilate To 65 g. of l-octanol heated at 108C. there was added 53.1 g. of N-methylisatoic anhydride in portions during 3.5 hours and the reaction mixture was further heated at 108C. for 1.75 hours after addition was completed. The reaction mixture was distilled to remove unreacted octanol and to afford the n-octyl N- methylanthranilate as the liquid distillate fraction, b.p. l 68C at less than 0.1 mm pressure.

EVALUATION OF PRODUCTS The compounds produced in accordance with this invention were blended into a synthetic ester oil lubricant (made by reacting pentaerythritol with an equimolar mixture of C and C monocarboxylic acids) and tested in an oxidation test in accordance with the following procedure.

A sample of the test composition is heated and air at the rate of about 5 liters per hour is passed through for a period of about 24 hours. Present in the test sample are specimens of iron, copper, aluminum, and lead. It should be noted that the metals are typical metals of engine or machine construction, and they also provide some catalysis for the oxidation of organic materials.

As will be seen from the tables that follow, two different measures of the antioxidant effectiveness of the additive are shown. One is change in acidity, determined in terms of change in neutralization number (ANN). Superiority of an additive over the untreated lubricant or over another additive is indicated by a smaller The usual criteria for determining the antioxidant activity of an additive in a lubricant include changes in acidity and viscosity. It is recognized in this art, howchange in acid number. The other measure is change in viscosity (AKV) and the smaller the noted change, the better is the additive.

ever, that while an additive may give control in these In the following, Table I summarizes the results ob- 5 two areas it y have little of no effect in Other areas. tained with the N-naphthyl anthranilates of this invensuch as in controlling sludge formation and lead loss.

tion; Table II shows the results obtained with the an- Furthermore; While the Single additive y be effecthranilate, the N-alkyl and the N-phenyl anthranilate five, more actlvlty y be required than can be TABLE I Viscosity, KV, l00F Final Acidity, NN Final ANN Wt. Temp., "F

Additive TABLE II Viscosity, KV, lO0F Final Acidity, NN Final ANN Wt. Temp, F

Additive .9 .4 .0666113bDDB NDJJJDAAJJJJJJJ .81 3444 9647006655 77776826oo76448669 56- 46 5 0 0 O O 5 0 0 0 5 0 5 0 2 5 5 5 5 2 5 5 5 2 5 2 5 4 4 4 4 4 4 4 4 4 4 4 4 4 6 m l H y e w e n m m h t a I. .l r h i n M h D. n a I O o n t O. y a r v. e a n X .m 0 h o m d d r a d 0 w n d m d a n m w. m n a a l n n n e .I. I I: y n h m a e m a M M h l h r 1 cc t y P 48 h M 6 t n x .t t im a m N Nu m m m ri l l l 1 v. TM V. y V. YN m N l h N I V. 1 h C I h n B W 2 O E O O c n .n h C 23 n 2 n na P D. 0

It can be seen from the above tables that in virtually tained with the additive above. In such cases it is someevery instance in which a direct comparison can be times advantageous to add another material. In the made (i. e., conditions of temperature and concentra- 65 present invention, it has been found that p-p'-dioctyltion the same) the N-naphthyl anthranilate is unexpectdiphenylamine (DODPA) may be used to advantage.

edly superior to those disclosed in the references dis- Consider the data below obtained at 450F in the cussed hereinabove. above ester lubricant.

i I Pb Additive by Wt. ANN AKV,% Loss Sludge l) n-octyl N'naphthyl- 4 1.34 35 9.7 nil anthranilate dium 2) 1) 1% DODPA 4 1.29 50 1.7 nil 2 1.94 49 1.4 nil I 9% of N-qclyl N napht hyl anthranilale It may be seen from the data with the anthranilate 10 the formula alone that the use of DODPA with n-octyl-N- COOCBHU naphthylanthranilate gives improvement not only in sludging (at 2 percent level) but also in the acid values and lead loss. Thus, at the 4 percent level of additive, sludging was not affected, but the lead loss was reduced considerably and there was a small reduction in acid value. The greatest effect of the second additive shown by the data is at the 2 percent level. Here sludging is reduced from a medium rating to nil, the lead loss is reduced about 23 mg. and the acid value is reduced significantly.

While the optimum amount of DODPA that may be used is not known, it is believed that DODPA may be used with the other additive in a ratio of from 4:1 to 1:4 when using a total additive concentration of from about 0.5 percent to about percent by weight.

I claim:

1. A lubricant composition comprising a major amount of a lubricant and an amount sufficient to impart antioxidant properties thereto of an ester of anthranilic acid having the formula:

4. The composition of claim 3 wherein the -C H group is nC l-l 5. The composition of claim 3 wherein the -C 1-l is 2,2,4-trimethylpentyl.

6. The composition of claim 1 wherein the ester has the formula a mixture C -C aliphatic monocarboxylic acids. 

1. A LUBRICANT COMPOSITION COMPRISING A MAJOR AMOUNT OF A LUBRICANT AND AN AMOUNT SUFFICIENT TO IMPART ANTIOXIDANT PROPERTIES THERETO OF AN ESTER OF ANTHRANILIC ACID HAVING THE FORMULA:
 2. The composition of claim 1 wherein said ester is present in an amount of from about 0.005 percent to about 15 percent by weight.
 3. The composition of claim 1 wherein the ester has the formula
 4. The composition of claim 3 wherein the -C8H17 group is n-C8H17.
 5. The composition of claim 3 wherein the -C8H17 is 2,2,4-trimethylpentyl.
 6. The composition of claim 1 wherein the ester has the formula
 7. The composition of claim 1 wherein the lubricant contains, in addition to said ester p,p''-dioctyldiphenylamine in a ratio to said ester of from 4:1 to 1:4 when using said ester and said p, p''-dioctyldiphenylamine at concentrations of from 0.5 percent to about 15 percent by weight.
 8. The composition of claim 1 wherein the lubricant is a lubricating oil.
 9. The composition of claim 8 wherein said oil is a synthetic ester oil.
 10. The composition of claim 9 wherein said synthetic ester oil is an oil made from pentaerythritol and a mixture C5-C9 aliphatic monocarboxylic acids. 